Heating and cooling buildings consumes a large amount of energy. This is particularly the case in climates where there is a great disparity between maximum summer and minimum winter temperatures, as in much of North America, where it is necessary that buildings are cooled in the summer and heated in the winter.
Buildings are cooled and heated by a variety of means, including air conditioning units, electric heaters, wood stoves, forced air gas furnaces, and hot water or steam radiators. It is generally the case that a constant indoor temperature is desired depending on the external temperature. For example, room temperature (a temperature at which humans are generally accustomed for indoor living) is typically between 64-74° F. (approximately 18-23.5° C.), however local climate conditions may acclimatise people to higher or lower temperatures.
To minimize heat transfer between a building and its surrounding environment, various construction techniques have been developed which minimize the amount of energy required to maintain constant indoor temperatures. Examples of such techniques include designing and using building materials and insulation with high values of thermal resistance (also known as R-values), and employing air-flow heat exchangers which minimize the amount of heat lost to the external environment in the winter and reduce the amount of heat gained from the external environment in the summer.
Another way to improve the energy efficiency of a building is to make use of available geo-thermal energy. As is well known, the ground temperature below the frost line in much of North America is a relatively stable 55-56° F. on average (approximately 13° C.) throughout much of North America, ranging from around 41° F. (5° C.) in northern climates to about 71° F. (21.6° C.) in southern climates.
Ground-source heat pumps are one well known type of technology which take advantage of this physical phenomenon. Heat pumps typically have a series of heat exchanging coils buried in the ground below the frost line. In warm summer months, water can be cooled to the ground temperature when circulating through these coils. This cooled water can then be circulated in radiators located inside the building to cool the interior space, among other applications. In a similar way, a building can be heated in the winter by warming the water in the heat exchanging coils. The disadvantage of this technology is that energy must be added into the system (usually in the form of electrical energy to run a compressor) as a heat pump utilizes the same operating principles and cycles as a refrigerator.
However, there has been a lack of construction technology specifically designed to take advantage of the fact that the ground surrounding and underlying a building can be used as a heat sink in the summer and a heat source in the winter.
Therefore, there is a need for building structures and techniques which reduce energy consumption by using the ground as a source of heat in the winter and as a heat sink in the summer.